A mesh network which includes mutually connected terminal devices (personal computers, PDAs, mobile phones, in-vehicle devices such as car navigation systems have been in practical use.
The mesh network can actively compose the network adjusted to changes that occur when each terminal device joins or leaves the network or moves within the network; that is, the mesh network has flexibility lacking in the conventional fixed network. At the same time, when the terminal moves or when the wireless communication environment changes because of obstruction, there is a possibility of the problem that the quality of transmission degrades and the path for transmitting data is cut out.
In order to address this problem, in the mesh network, one path is actively selected among multiple transmission paths (also simply referred to as path) for use in transmitting data. The network in which the transmission paths are actively controlled is generally known as an ad hoc network.
Technologies for selecting preferable paths for highly reliable and high-quality data transmission in the ad hoc network have been known (for example, see Patent Literature 1 and Patent Literature 2).
Patent Literature 1 discloses a technology that collects the path information (for example, the number of retry and value indicating the load on a line) regarding the status of the relay on each path by transmitting the path examining frame to paths to the destination before or during the data transmission, determines the path to be used before the data transmission, using the collected path information. The technology also allows detecting the malfunction during data communication and switching the paths.
Patent Literature 2 discloses a technology for obtaining the total amount of traffic which causes delayed packets relayed by the relay included in the path, by transmitting a predetermined packet to each path, and, for transmitting the packets, using the path with smallest total amount of the obtained traffic.
[Citation List]
[Patent Literature]
    [Patent Literature 1] Japanese Unexamined Patent Application Publication No. 2001-136178    [Patent Literature 2] Japanese Unexamined Patent Application Publication No. 2005-347879